The invention relates to a method for gear grinding and/or gear honing of noise-optimized gears on a gear-cutting machine, to the associated measuring method and to the control software for the corresponding control of the gear-cutting machine.
The demands on modern transmissions with respect to construction size, noise behavior and transferrable powers are increasing more and more. The demands on the production precision of the installed gear wheels thus also increase inter alia. To satisfy these demands, the gear wheels are provided in many cases in manufacture with a targeted modified flank geometry which differs from the purely involute flank geometry. The modifications are designed in this respect such that they positively influence the running smoothness and the transfer behavior of the transmission under load pressure conditions.
The running noise of a transmission is determined at crucial points from the excitation or from the vibration behavior of the gear under the currently active load pressure conditions or from the time development of the tooth force in the respective tooth meshing. The vibration excitation of a spur gear pair under load and at sped represents an irregularity in the rotational movement between the pinion and the wheel. This irregularity can be described with reference to a variable path transmission, to the rotational distance difference or to the rotational distance error. The rotational distance difference or the rotational distance error is a function of the gear geometry and of the elastic behavior of the overall transmission system. The influence of the gear geometry on the excitation behavior is decisively determined by main geometrical characteristics such as the transverse contact ratio or the overlap ratio as well as by the shape of the tooth flank topology and by manufacturing tolerances.
It has now been recognized as the result of different research projects that, in addition to factors such as overlap ratio, pitch precision, tip reliefs and root reliefs at the gears, periodic corrections in the form of waviness on the flanks of a gear also have a positive influence on the noise excitation of a gear under load pressure conditions.
Calculation programs were prepared for this purpose in the different research projects with whose aid the influences of tooth modifications and tooth corrections on the running behavior and noise behavior of spur gear pairs were able to be simulated. In order now to carry out the calculation of a low-noise gear pair, a great deal of detail knowledge coupled with empirical investigations is required. The calculated results have to be converted into correction values and modification values or have to be implemented in a CNC machining program for the gear-cutting machine. The gear-cutting machine ultimately has to be capable of transferring these corrections very exactly onto the respective tooth flank.
As already previously described, in addition to macrogeometrical tooth flank corrections and tooth flank modifications in the range of several micrometers which primarily positively influence engagement shock and the disengagement shock of the gear mesh, microcorrections (flank waviness) on the tooth flanks are also necessary which have the result of a low-noise tooth meshing of the tooth pairs.
Gear-cutting machines with which corrections of the tooth flanks can be carried out are generally already known.
For instance, the method of profiling a worm grinding wheel with a three-dimensionally modified width zone is also described in addition to a grinding tool and the associated profiling tool in DE 10 2004 057 596, for example. The objective here is an increased degree of use of the worm grinding wheel width. Using a profiling gear in accordance with this description, 3-dimensional corrections on the tooth flanks are first able to be transferred to the worm grinding wheel and from there onto the ground workpiece again This type of profiling is, however, very inflexible since first a suitable 3-dimensionally corrected profiling gear has to be produced so that then its surface structure can in turn be transferred via the worm grinding wheel to the finished gear. Modifications to the profiling gear are very labor-intensive and can thus not be implemented in the short term in a mass-production process.
Documents DE 197 06 867 A1 and DE 37 04 607 each describe a method for the diagonal gear cutting of gears in order thus to produce corrections on the tooth flanks in dependence on the gear width. This is a tried and trusted method to directly produce or reduce interleaving on the flanks of a gear above all with spherical helical gears. For this purpose, the angle of engagement of the worm grinding wheel on the right/left worm flank is continuously varied from one end of the tool to the other and the tool is shifted in the axial direction of the tool during the grinding process in accordance with the workpiece width position. This process is, however, not sufficient alone directly to produce waviness on the tooth flanks of a ground gear. A surface modification of the dressing tool and/or of the worm grinding wheel over the tooth height is required for this purpose. Optionally, even additional axial movements of the gear-cutting machine are required.
DE 195 17 359 relates to the machining of a bevel gear pair, wherein one of the gear partners is ground and the other is honed to achieve a low-noise running noise in the transmission. This is already known in spur gear transmissions. The surface structure of a ground gear extends in the flank direction of the gear, that of a honed gear has a comma-shaped structure. These different directions of the surface structure on the tooth flanks have properties which are considerably smoother in running than two toothed wheels which were machined using the same hard-fine machining processes when they roll off one another. However, the combination of the two machining methods alone is not sufficient for the increased demands made today on the smooth running of a gear in a transmission. Still further measures rather additionally have to be taken.
A method of partial gear grinding of tooth flanks with periodic tooth flank modulation is described in DE 10 2010 026 412 A1. In this method, the tool is guided along the tooth flank in repeated stroke movements, with a delivery taking place in the normal direction between each stroke movement of the tool and the workpiece not carrying out any hob movement during the single stroke. The number of required stroke movements for machining an individual tooth flank and the associated high time effort per workpiece are disadvantageous in this method.
It is already known in this respect that the same waviness without phase shifts on the tooth flanks of the mutually meshing gears as a rule produces much lower noise excitations at all teeth on the rolling off add are thus less noise-critical than workpieces having complementary waviness.
It is furthermore known that an angle of rotation of the toothed wheel can be associated with each point on the tooth flank and characterizes its position on the rolling off. Conversely, the measurement of the angle of rotation or in this case the angle of rotation error can now be traced back to points on the tooth flanks. If therefore now the rotational distance error of the gear is recorded, regions result in which the angle of rotation is too small or too large with respect to the value which can theoretically be calculated, that is regions at which the rotational movement leads or lags. This irregularity of the rotational movement results in a vibration excitation of the transmission system.